Aiming at the problems of high boulder yield, high explosive consumption and poor blasting effect in an open-pit mine with complex lithology in Xinjiang, 59 blasting tests for the optimal inter-hole and inter-row delays in rock masses with different blastabilities were carried out on four levels (between 445 m and 595 m) at the east side of the mine. The optimal delays between holes and rows were determined by the shape of blasting pile, ore rock fragmentation and powder factor. The test results show that the blasting pile is flat and the fragmentation is uniform for benches of mudstone with some fine sands when the delays between holes and rows are 5.9 ms/m and 14 ms/m, respectively. For sandstone with part of mudstone lithologic, when the delays between holes and rows are taken as 2.7 ms/m and 14.2 ms/m respectively, the blasting pile shape and fragmentation are reasonable and the boulder yield is low. The test results are applied to the field production of the mine, and the average powder factor and boulder yield are 4.03% and 1.8%, respectively, which are lower than those of previous years. The research shows that reasonable selecting of delay time between holes and rows for complex geological conditions can obtain flat blasting pile and the uniform block size, which can effectively reduce the powder factor, and save costs. The delay time determined in this test can provide important field data for selecting the delay time of mudstone and sandstone mixed bench blasting under the same geological conditions in Zhundong area.

Experiments of vented explosion were conducted in a 1 m³ vessel under the conditions of top ignition for premixed methane-air gas with a concentration from 7% to 13% to investigate the influence law of methane concentration on flame evolution and internal overpressure during the vented explosion process. The explosion venting mechanism was analyzed by analyzing the pressure-time curve and the flame evolution image. The results prove that concentration has a significant impact on the explosion venting characteristics of the methane-air premixed gas. The overpressure inside the container presents a double-peak phenomenon with a specific methane concentration. The first pressure peak P₁ can appear at each concentration, while the second pressure peak P₂ only occurs when the concentration is 9%. P₁ increases first and then decreases with the increase of concentration, while the trend of the timing of the peak is the opposite. However, both reach the extreme value at the methane concentration of 10%. This is mainly formed by the combined effects of initial flame propagation, external explosion, Helmholtz oscillation and Taylor instability, etc. The phenomenon that P₂ is much higher than P₁ is mainly formed by the mutual promotion of flame and sound pressure and the thermoacoustic coupling effect triggered by disturbance. The flame downward propagation velocity increases first and then decreases with the concentration, and reaches the maximum value when the methane concentration is 10%, and the combustion velocity is generally faster in the slightly rich combustion state.

The reasonable selection of the incision angle is an important factor for the success of blasting demolition of a typical reinforced concrete chimney. In order to determine the selection range of incision angle, the isolation method was adopted to establish a theoretical model according to the force and failure characteristics of the residual section. The solution formula of any angle position on the residual section was derived, and a revision coefficient k was defined to express the influence of the cylinder at the upper part of the unnotched section. Furthermore, the stress and bending moment conditions of the dumping cylinder were established, and the selection range of the incision angle was obtained by combining the solution formula and the damping conditions. The case study shows that with the increase of the incision angle, the maximum tensile stress, the maximum compressive stress and the bending moment generated by the upper cylinder of the incision tend to increase, while the resistance moment of the residual section tends to decrease. The upper limit of the selection of the incision angle can be obtained when the maximum tensile stress reaches to the material strength limit, and the lower limit can be determined when the two bending moments are equal. Changing the incision angle would have a greater effect on stress than changing the incision height. Under the condition that the actual incision height is 4.5 m in the engineering case, the selection range of incision angle based on the established theoretical model is 198°~237.6°, and the actual incision angle is 216° within the theoretical selection range, which further verifies the reliability of the theoretical model. More extensive application and guide engineering practice are expected.

To study the complex mechanical movement and accumulation process of broken blocks in the process of underwater rock bench blasting, a fluid-solid coupling numerical calculation method based on FLUENT-EDEM was adopted. Firstly, the parallel bond and Hertz-Mindlin contact model were introduced between the particles, and the parameters of the parallel bond were calibrated by comparing the results of Brazilian splitting experiment and numerical calculation. Furthermore, the underwater bench blasting model was established, and the mechanical action mechanism of water on rock mass breaking and movement was analyzed. Finally, the whole ejection process of particles from a submerged step block was studied, and characteristics of the block velocity, block stacking and flow field were discussed. The results show that the accumulation and stratification of block particles are related to their initial velocity and height, and the horizontal movement distance of the block particles in the middle step is the biggest under the explosion load action. Meanwhile, the block particles in the upper blocking part mainly roll and cover the middle block particle layer under the action of gravity and buoyancy, which are less affected by the explosion load. Additionally, the explosion energy is mainly used to break the rock at the initial detonation stage, and the water has no obvious flow velocity. With the bulging and throwing movement of block particles, the fluid streamline velocity near the front surface of the bench is largest. When the block particles start to roll and slide, the streamline is mainly affected by the movement form of the particles. Therefore, the fluid-solid coupling model by Fluent-EDEM can accurately simulate the block motion in the underwater bench blasting, which can provide a new research method for underwater rock blasting engineering.

In order to further study the propagation characteristics of surge wave induced by underwater blasting loads, the multi-physical field coupling simulation method powered by the dynamic analysis software COMSOL was adopted to establish a transient solution model based on the second water source project-diversion project of Guilin City. The isosurface, peak stress and vibration velocity of surge wave under explosion load were studied and evaluated based on field monitoring results. The results show that the surge wave produced by underwater blasting essentially propagates around the center of the blast center, and the surge isosurface evolves from regular round to irregular ellipsoid with time. The surge waves decay rapidly during propagation, and with the increase of water medium velocity threshold, the influence range of surge wave action region is small. In addition, the stress of the surge wave has superposition effect under the condition of delayed blasting, and thus there are multiple peaks. When the distance to blast center increases from 28 m to 108 m, the attenuation rate of the peak vibration velocity of the surge wave reaches 96.3%, which has little effect on the structure. Meanwhile, the time of the peak velocity of the surge wave increases gradually with the increase of the distance to blast center.

Aiming at the construction problems of a subway tunnel adjacent existing buildings in the section between Jialingjiang Road station and Xiangjiang Road station of Qingdao Metro Line 13, a new construction scheme of mechanical excavation combined with blasting is proposed. In the scheme, bench method is used with the upper bench in the weak stratum excavated by mechanical method, and the lower bench in the hard stratum excavated by blasting method. Furthermore, the vibration velocities of the adjacent buildings caused by the proposed scheme and the traditional full-section blasting scheme are analyzed and compared by using FLAC3D and blasting equivalent load method. The results show that, the peak vibration velocity of each monitoring point under the mechanical-blasting scheme decreases significantly compared with the full-section blasting with the maximum reduction rate of 61.1% which is within the allowable range and validates the new scheme. The construction parameters of the mechanical-blasting scheme are compared and selected based on the building settlement, plastic zone of surrounding rock mass, vibration velocity of the buildings, etc. Finally, the mechanical excavation advance of the upper bench is determined to as 0.5 m. Besides, the construction effect of the optimized parameters is monitored and evaluated. The mechanical-blasting construction scheme successfully solved the problems encountered in the project, and shortened the expected construction period by 3 months, which shows the rationality of the proposed construction scheme and parameters, as well as the validity of the calculation results.

Perimeter blasting is very important to control engineering quality in the process of roadway construction, and it is a common way to use slotted pipe blasting to improve the perimeter blasting effect. However, the unreasonable setting of slotted pipe blasting parameters still weakens the directional destruction effect, including the greatly damaged contour, low hole retention rate, common phenomena of over-excavation and under-excavation. In order to improve the directionality of blasting damage, the slotted pipe blasting parameters should be optimized. The reasonable blasting parameters were determined with the study of explosive slotted pipe uncoupling and different initiation positions by numerical simulation using ANSYS/LSDYNA. According to the numerical simulation results, the balance between the protection of surrounding rock mass and directional failure can be achieved when the uncoupling coefficient between the explosive and slotted pipe is 1.12. Meanwhile, the integrity of the contour line is greatly improved when the initiation positions of two adjacent explosives are changed to make the meeting position of the explosive shock waves on the same horizontal plane that shifted to 3/4 of the position between two blast holes. It can be concluded that the damage to the retained rock mass can be greatly reduced as adopting uncoupled structure between slotted pipe and charge, and changing the meeting position of stress wave between blast holes by adjusting the detonation position of charge.

In order to improve the analysis accuracy of loosening blasting vibration signals, a hybrid denoising method based on local mean decomposition (LMD), multiscale fuzzy entropy (MFE), and singular value filtering (SVD) was established. Firstly, the vibration signal was decomposed by LMD method to obtain a series of product components (PF). Then, the blasting vibration signal was preliminarily denoised by calculating MFE and correlation coefficients. Finally, the real signal components were denoised and extracted by SVD filtering on the residual noise of the main PF components. The results show that the proposed LMD-MFE-SVD denoising method can effectively deal with the noisy PF components. For the simulated signal with multiple components with noise, the LMD algorithm is more efficient than the EMD algorithm. Furthermore, the signal-to-noise ratio (SNR), root mean square error (RMSE) and percentage of distortion (PRD) of the proposed LMD-MFE-SVD method are significantly improved by 11.73%, 22.07% and 9.25%, respectively, compared with the LMD algorithm, which indicates that the noise reduction efficiency is considerable. According to the waveform and spectrum comparison of the measured loosening blasting vibration signal after denoising by the proposed LMD-MFE-SVD method, the denoised signal waveform is more concentrated with most of the signal information retained. The frequency spectrum is clearer, and the signal frequency peaks are effectively displayed.

In order to study the protective performance of minesweeper protective equipment on the chest and abdomen under the action of explosion shock wave, it is necessary to explore efficient test methods to improve the experimental research index system and overall performance of individual soldier protective equipment. In this paper, two sets of minesweeper protective equipment were taken as experimental research objects, and the real explosion test of minesweeper EOD operators for typical kneeling posture was designed based on Hybird III dummy model under different sealing conditions. The shock wave was generated by the explosion of 50 g TNT charge column. Two wall overpressure sensors were installed in the chest and abdomen of the dummy model to measure the shock wave overpressure generated by four real explosion tests, and a free field pressure sensor was set at the same distance relative to the explosion source to compare the test data. Using the dummy data acquisition system, the whole process data of overpressure on the chest and abdomen after the shock wave penetration of the minesweeper protective equipment were obtained. Through data processing, the pressure-time curve of chest and abdomen subjected to explosion impact and the peak attenuation rate of overpressure were obtained and compared. The test results preliminarily verify that the better the sealing performance of the joint, the higher the protection performance, which indicates that the protective equipment with high sealing performance has a certain blocking attenuation effect on the diffraction of explosion shock wave, and can reduce the damage caused by superimposed overpressure to the chest and abdomen to a certain extent. The experimental design and data analysis in this paper can be used for further equipment performance improvement.

Distortion phenomenon would occur in time-frequency analysis when Hilbert-Huang Transform (HHT) is used to process the blasting seismic signal mixed with noise. In order to improve the analysis performance for noisy blasting seismic signals, the factors affecting the accuracy of time-frequency analysis of HHT were improved through an improved algorithm. Firstly, the empirical mode decomposition (EMD) was improved by the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) to suppress the low-frequency trend terms. Furthermore, the multiscale permutation entropy (MPE) code was added to control the high-frequency noise. Finally, the normalized Hilbert transform (NHT) was performed on the IMFs obtained by CEEMDAN·MPE. Through the above three steps, the problem of insufficient precision in the time-frequency analysis of noisy blasting seismic signals by the traditional HHT can be improved. In order to verify the accuracy of the CEEMDAN·MPE-NHT algorithm, a comparative study on the HHT and CEEMDAN·MPE-NHT algorithm was carried out, and the CEEMDAN·MPE-NHT algorithm was used for underwater drilling blasting seismic signals. The results show that the time-frequency spectrum of the IMF decomposed by CEEMDAN·MPE and processed by NHT has a greatly improved high resolution compared with HHT in both time and frequency domain. The research results can be used for identifying and controlling the hazards of blasting seismic waves.